disable 'import-mode' when using global sort #60361
Description
Enhance
'import mode' is enabled previously to avoid TiKV into write stale and flow control, to make import success even through there are a lot of range overlap and some SST might ingested into L0, but with global sort, we can make sure there is no range overlap, it shouldn't ingest into L0 normally, we can disable switching to 'import mode' in this case